Glass packaging ensuring container integrity

ABSTRACT

A strengthened glass container or vessel such as, but not limited to, vials for holding pharmaceutical products or vaccines in a hermetic and/or sterile state. The strengthened glass container undergoes a strengthening process that produces compression at the surface and tension within the container wall. The strengthening process is designed such that the tension within the wall is great enough to ensure catastrophic failure of the container, thus rendering the product unusable, should sterility be compromised by a through-wall crack. The tension is greater than a threshold central tension, above which catastrophic failure of the container is guaranteed, thus eliminating any potential for violation of pharmaceutical integrity.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of U.S. patent application Ser. No. 15/814,917 filed Nov. 16, 2017 and entitled “GLASS PACKAGING ENSURING CONTAINER INTEGRITY” which itself is a divisional of U.S. patent application Ser. No. 13/778,975 filed Feb. 27, 2013, which claims the benefit of priority under 35 U.S.C. § 119 of U.S. Provisional Application Ser. No. 61/604,647 filed on Feb. 29, 2012, the contents of all of which are relied upon and incorporated herein by reference in their entireties.

BACKGROUND

A concern for food and drug manufacturers is maintaining the sterility of package contents from failing during transport and storage until patient use. While glass containers are superior to many alternative materials, they are not unbreakable and occasionally experience damage from handling and transport. Cracks are severe damage that extend through the wall thickness, compromising content sterility but not leading to catastrophic failure of the package. Such cracks may result in recalls when detected by a health care professional or end consumer at the point of use, and can be costly to the pharmaceutical or foodstuff manufacturer.

SUMMARY

The present disclosure provides a strengthened glass container or vessel such as, but not limited to, vials for holding pharmaceutical products or vaccines, and foodstuff containers (e.g., bottles, baby food jars, etc.) in a hermetic and/or sterile state. The strengthened glass container undergoes a strengthening process that produces compression at the surface and tension within the container wall. The strengthening process is designed such that the tension within the wall is great enough to ensure catastrophic failure of the container, thus rendering the product unusable, should sterility be compromised by a through-wall crack. The tension is greater than a threshold central tension, above which catastrophic failure of the container is enhanced, thus significantly reducing or eliminating any potential for violation of container integrity.

Accordingly, one aspect of the disclosure is to provide a glass article including a first surface and a second surface separated by glass having a thickness of from 1.0 mm to 1.2 mm. The glass may be an ion-exchanged aluminosilicate glass comprising at least one alkali metal oxide. The glass article has a first region under a compressive stress, the first region extending from at least one of the first surface or the second surface to a depth of layer in the glass, and a second region under a central tension greater than 13 MPa, the second region extending from the depth of layer. The central tension is sufficient to allow self-propagation of a flaw front from the first surface to the second surface and laterally across the first surface. Self-propagation of the flaw front from the first surface to the second surface and laterally across the first surface may render the article unsuitable for its intended use.

A second aspect of the disclosure is to provide a container comprising a glass. The container has a thickness, a first surface, and a second surface. The glass has a first region under a compressive stress, the first region extending from at least one of the first surface and the second surface to a depth of layer in the glass, and a second region under a central tension, the second region extending from the depth of layer into a central region of the glass. The central tension or equivalent measure of integrated central tension or stored elastic energy is greater than a threshold tensile stress value. The central tension may be greater than 13 MPa.

A third aspect of the disclosure is to provide a method of making a glass article having a first surface and a second surface separated by a thickness. The method includes forming a first region in at least one surface the glass, the first region extending from at least one of the first surface and the second surface to a depth of layer in the glass. The first region is under a compressive stress. The method further includes forming a second region under a central tension of at least 13 MPa, the second region extending from the depth of layer. The central tension of at least 13 MPa is sufficient to allow self-propagation of a flaw front from the first surface to the second surface and laterally across at least the first surface.

A fourth aspect of the disclosure is to provide a method of ensuring self-elimination of a vessel having an intended use. The method includes providing the vessel, the vessel comprising a glass, the vessel having a thickness and first surface and a second surface. The glass may include a first region may under a compressive stress, the first region extending from at least one of the first surface and the second surface to a depth of layer in the glass. The glass may also include a second region under a central tension of at least 13 MPa, the second region extending from the depth of layer. The central tension is greater than a threshold tensile stress that is sufficient to allow self-propagation of a flaw front through the thickness from the first surface to the second surface. Self-propagation of the flaw front from the first surface to the second surface renders the vessel unsuitable for its intended use.

These and other aspects, advantages, and salient features will become apparent from the following detailed description, the accompanying drawings, and the appended claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional schematic view of segment of a strengthened container wall;

FIG. 2 is a photograph of a glass container that has experienced a through-thickness crack without catastrophic failure;

FIG. 3 is a photograph of flaw propagation behavior in under-stressed and critically-stressed or frangible glasses;

FIG. 4 is a plot of the dependence of critical/catastrophic flaw growth in ion-exchanged glass as a function of central tension;

FIG. 5 is a schematic plot of insult force versus central tension showing possible breakage modes;

FIG. 6 is a schematic diagram of a drop test;

FIG. 7 is a plot of failure mode rate for dropped and bottom glass vials comparing breakage behavior for ion-exchanged alkali aluminosilicate glass and non-ion-exchanged borosilicate glass;

FIG. 8 is a plot of failure mode rate of glass vials as a function of central tension (corrected for stress optical coefficient (SOC), using the triangle method);

FIG. 9 is a plot of failure rate as a function of drop height;

FIG. 10 is a schematic diagram of testing configuration for introducing deep damage to glass articles in Examples 2-4; and

FIG. 11 is a schematic diagram of a cartridge.

DETAILED DESCRIPTION

In the following description, like reference characters designate like or corresponding parts throughout the several views shown in the figures. It is also understood that, unless otherwise specified, terms such as “top,” “bottom,” “outward,” “inward,” and the like are words of convenience and are not to be construed as limiting terms. In addition, whenever a group is described as comprising at least one of a group of elements and combinations thereof, it is understood that the group may comprise, consist essentially of, or consist of any number of those elements recited, either individually or in combination with each other. Similarly, whenever a group is described as consisting of at least one of a group of elements or combinations thereof, it is understood that the group may consist of any number of those elements recited, either individually or in combination with each other. Unless otherwise specified, a range of values, when recited, includes both the upper and lower limits of the range as well as any ranges therebetween. As used herein, the indefinite articles “a,” “an,” and the corresponding definite article “the” mean “at least one” or “one or more,” unless otherwise specified.

Referring to the drawings in general and to FIG. 1 in particular, it will be understood that the illustrations are for the purpose of describing particular embodiments and are not intended to limit the disclosure or appended claims thereto. The drawings are not necessarily to scale, and certain features and certain views of the drawings may be shown exaggerated in scale or in schematic in the interest of clarity and conciseness.

Glass is a preferred material for pharmaceutical packaging for several reasons, including optical clarity, hermeticity, and chemical inertness. However, it is possible for a glass package to exhibit a through-thickness crack which can destroy the contents' hermeticity or sterility and yet still effectively contain the drug. The primary concern for this defect is possible unawareness of the pharmaceutical recipient of the non-sterility of the pharmaceutical which may, in some instances, lead to ineffectual medicinal dosage and adverse health consequences.

Described herein are a glass container, glass article, and method to ensure self-elimination of the containers and articles and the rendering of the contents such as, for example, a pharmaceutical, contained therein unusable, when propagation of flaws potentially violates the integrity of the container. As used herein, terms such as “container” and “vessel” refer to any article that is adapted to hold a solid or fluid for storage. The container may, in some embodiments, be sealable. The container, article, and method rely on the release of stored elastic energy in the walls of the container to cause self-propagation of flaws that extend into the central tension region of the glass. Flaws will not propagate when experiencing a net compressive stress, and only propagate when an applied tensile stress is great enough to break bonds at the flaw tip.

A container or vessel, such as a vial for holding sterile substances such as vaccines, biologics, pharmaceuticals, foodstuffs, solutions, or the like in which super-critical flaw growth through the thickness of the container wall and laterally across the container surface destroys the integrity of the container, is provided. Non-limiting examples of such containers include glass vials, bottles, food jars, cartridges, syringes, ampules, or the like. The container comprises a glass. The container has at least one wall having a thickness t, a first surface, and a second surface. The at least one wall is strengthened, and the first and second surfaces are each under a compressive stress CS. The regions under compressive stress, also referred to herein as the “compressive layers,” extend from the first and second surfaces, respectively, to a depth of layer DOL within the container wall. The compressive stress in the compressive layers is balanced by tensile stress, also referred to herein as “central tension” or “CT,” in a central region of the wall. The central tension CT is greater than a threshold tensile stress at which flaw front propagation and subsequent bifurcation or splitting—also referred to herein as “multiple flaw branching”—in the glass occurs and the central tension alone (i.e., absent external stresses) is sufficient to assure destruction of the glass and the container into multiple pieces. Under such conditions, multiple flaw propagation and branching resulting in container failure occurs within a relatively short time (typically less than 24 hours), as opposed to other mechanisms, such as fatigue or the like, which may result in container failure over the span of days. In some embodiments, destruction of the container due to the above mechanism occurs in less than about one hour. In some embodiments, the threshold tensile stress is sufficient to allow self-propagation of a flaw and/or multiple branching of the flaws (flaw branching) through the entire thickness of the glass from the first surface to the second surface of the container. Such flaw splitting ensures that a breach of the integrity of the container does not go unnoticed and elimination of such “closed container integrity” (CCI) violations. While the above descriptions describe a delay between the “insult” and the “failure event,” it should be understood that at no time during this delay is the sterility compromised prior to the failure event; i.e., at no point is a through-crack stable prior to container failure.

The introduction of compressive stress into a glass container or vessel surface will increase mechanical performance of the final product. If the stored energy is great enough, flaws penetrating deeper than the compressive layer and into the tensile layer will spontaneously propagate both through the wall thickness and laterally across the wall, leading to complete failure and destruction of the contents of the container or vessel.

A cross-sectional schematic view of a segment of the strengthened container wall is shown in FIG. 1. Container wall 100 comprising at least one glass has a thickness t, first surface 110, and second surface 112. Container wall 100 has a nominal thickness t of up to about 6 mm. In some embodiments, thickness t is in a range from 0.05 mm up to about 4 mm, in other embodiments, in a range from about 0.3 mm to about 2 mm, in other embodiments, in a range of from 0.8 mm to 2.0 mm, and in still other embodiments, in a range from about 0.9 mm to about 1.7 mm. It is understood that complex packaging geometries such as vials, cartridges, and bottles may have a variety of wall thicknesses throughout the container. While the embodiment shown in FIG. 1 depicts container wall 100 as a flat planar sheet, container wall 100 may have other configurations, such as three dimensional shapes or non-planar configurations. Container wall 100 has a first compressive layer 120 extending from first surface 110 to a depth of layer d₁ into the bulk of the container wall 100. In the embodiment shown in FIG. 1, container wall 100 also has a second compressive layer 122 extending from second surface 112 to a second depth of layer d₂. Depths of layer d₁, d₂ also refer to the depth at which the stress changes from negative (compression) to positive (tension). Container wall 100 also has a central region 130 that extends from d₁ to d₂. Central region 130 is under a tensile stress or central tension (CT), which balances or counteracts the compressive stresses of first and second compressive layers 120 and 122. The depth d₁, d₂ of first and second compressive layers 120, 122 protects the container wall 100 from the propagation of flaws introduced by sharp impact to first and second surfaces 110, 112 of container wall 100, while the compressive stress minimizes the likelihood of a flaw penetrating through the depth d₁, d₂ of first and second compressive layers 120, 122. In some embodiments, the compressive stress CS in each of first region 120 and second region 122 is at least about 200 MPa and, in other embodiments, at least about 500 MPa. In some embodiments, each of depths of layer d₁, d₂ is at least about 30 μm and, in some embodiments, at least about 50 μm. In other embodiments, the depths of layer d₁, d₂ are between 15 and 25% of the wall thickness t. The relationship between CS and central tension CT is given by the expression:

$\begin{matrix} {{CT}_{erfc} = {\frac{{CS} \cdot {DOL}_{FSM}}{t - \frac{2 \cdot {DOL}_{FSM}}{\alpha \cdot \sqrt{\pi}}} \times \left( \frac{2}{\alpha \cdot \sqrt{\pi}} \right)}} & (1) \end{matrix}$

In equation (1), DOL_(FSM) is the depth of layer in millimeters measured according to the FSM method described below, t is the thickness of the glass, and α is a constant equal to 1.37. Unless otherwise specified, central tension CT_(erfc) and compressive stress CS are expressed herein in megaPascals (MPa), whereas thickness t and depth of layer DOL are expressed in millimeters. The depth of the compression layer DOL and the maximum value of compressive stress CS that can be designed into or provided to a glass article are limited by frangible behavior; i.e., forceful or energetic fragmentation of the glass upon fracture.

Compressive stress and depth of layer are measured using those means known in the art. Such means include, but are not limited to, measurement of surface stress (FSM) using commercially available instruments such as the FSM-6000, manufactured by Luceo Co., Ltd. (Tokyo, Japan), or the like, and methods of measuring compressive stress and depth of layer are described in ASTM 1422C-99, entitled “Standard Specification for Chemically Strengthened Flat Glass,” and ASTM 1279.19779 “Standard Test Method for Non-Destructive Photoelastic Measurement of Edge and Surface Stresses in Annealed, Heat-Strengthened, and Fully-Tempered Flat Glass,” the contents of which are incorporated herein by reference in their entirety. Surface stress measurements rely upon the accurate measurement of the stress optical coefficient (SOC), which is related to the birefringence of the glass. SOC in turn is measured by those methods that are known in the art, such as fiber and four point bend methods, both of which are described in ASTM standard C770-98 (2008), entitled “Standard Test Method for Measurement of Glass Stress-Optical Coefficient,” the contents of which are incorporated herein by reference in their entirety, and a bulk cylinder method.

The glass of the container wall 100 is strengthened by the introduction of a compressive stress. These compressive stresses must first be overcome before encapsulated flaws in the glass will experience enough tension to propagate. Such compressive stress may be introduced, for example, by thermal tempering, chemical tempering by ion exchange, lamination of glasses or glasses and plastics (e.g., glass/glass or glass/plastic/glass lamination) having different moduli and/or coefficients of thermal expansion (CTE), and/or coatings of materials having moduli and/or CTE that differ from those of the glass. In some embodiments, the glass (or glasses) forming outer regions 120, 122 of glass container 100 has a CTE that is less than that of the glass (or glasses) forming the central region of container 100. Similarly, the glass (or glasses) forming outer regions 120, 122 of glass container 100, in some embodiments, has a Young's modulus that is greater than that of the glass (or glasses) forming the central region of container 100. In some embodiments, the coating is a high-modulus coating comprising at least one inorganic material such as, but not limited to, alumina (Al₂O₃), silica (SiO₂), combinations thereof, or the like.

One consequence of the introduction of compressive stress is the complementary buildup of tensile stress in opposing regions of the container. For physical force balance to be maintained, the amount of stored elastic energy (SEE) in both compressive (e.g., 120, 122 in FIG. 1) and tensile (e.g., 130 in FIG. 1) regions (compression and tension) must be equal. In most cases, the glass surface experiences a large compressive stress, and the interior experiences a smaller magnitude tensile stress. Accordingly, the large compressive stress at the surface is focused over a shallow depth, while the smaller tensile stress is distributed over the entire container wall thickness.

The stored compressive stress of both compressive regions (120, 122 in FIG. 1) is balanced by stored tension in the central region (130) of the glass, the allowable upper limit of which is set by the frangibility limit for a given glass thickness. The frangibility limit and frangibility are described in U.S. Provisional Patent Application No. 61/657,279, filed on Jun. 8, 2012, by Kristen L. Barefoot et al., entitled “Strengthened Glass Articles and Method of Making,” the contents of which are incorporated herein by reference in their entirety. As described in the above-referenced application, frangibility or frangible behavior is characterized by at least one of: breaking of the strengthened glass article (e.g., a plate or sheet) into multiple small pieces (e.g., ≤1 mm); the number of fragments formed per unit area of the glass article; multiple crack branching from an initial crack in the glass article; and violent ejection of at least one fragment a specified distance (e.g., about 5 cm, or about 2 inches) from its original location; and combinations of any of the foregoing breaking (size and density), cracking, and ejecting behaviors. The terms “frangible behavior” and “frangibility” refer to those modes of violent or energetic fragmentation of a strengthened glass article absent any external restraints, such as coatings, adhesive layers, or the like. While coatings, adhesive layers, and the like may be used in conjunction with the strengthened glasses described herein, such external restraints are not used in determining the frangibility or frangible behavior of the glass articles. The CT_(limit) for strengthened glass in which the compressive stress profile is characterized by a single complementary error function for a given thickness t of glass can be determined by the equation

CT _(limit)(MPa)=9.0(MPa/mm)·ln(t)(mm)+49.3(MPa/mm)·ln²(t)(mm),  (2)

where the CT_(limit) is in units of MPa, glass thickness t is in units of mm and less than or equal to about 1 mm, and ln(t) is the natural logarithm (base e) of the thickness t. The integrated central tension (ICT), which is the tensile stress integrated over the entire region under tension (i.e., from d₁ to d₂ in FIG. 1) may also be used to characterize fragmentation behavior.

Alternatively, the stored elastic energy density (SEE) within tensile region of the glass may be used to define fragmentation behavior. The stored elastic energy is given by the equation

SEE=(CT ² /E)·(t−2DOL)·(1−v),  (3)

where E is Young's modulus, t is the thickness of the container wall, v is the Poisson's ratio of the material, and the depth of layer DOL is the depth at which the stress changes from positive (compression) to negative (tension).

Flaws propagate under applied tensile stresses, and energy is consumed in the creation of new surface area generated by propagation of the flaw or crack. In unstrengthened glasses, energy may be dispersed in flaw propagation—including through-thickness propagation—but the flaw growth will stop upon removal or consumption of the applied stress. This is the mechanism for creation of the flaw shown in FIG. 2. The glass package in FIG. 2 experienced a through-thickness crack 200 without catastrophic failure. The package contents are considered non-sterile and unfit for use due to the presence of crack 200.

In the case of strengthened glass, it is possible to engineer the stored elastic energy or corresponding central tension to be great enough so that flaw fronts which extend into the tensile region will self-propagate to cause complete separation of glass and catastrophic failure of the container. This is often characterized by flaw front bifurcation/flaw-front splitting, where the central tension alone—absent external stresses—is sufficient to ensure destruction of the glass package into multiple pieces. Photographs of flaw propagation behavior in under-stressed (A) and critically-stressed or frangible (B) glasses are shown in FIG. 3. In critically-stressed glass (B), any flaw induced deeper than the depth-of-layer (into the central tension region) will propagate catastrophically, whereas in the under-stressed glass (A), propagation of the flaw produces only a single crack. In the typical non-stressed case (A), if the single crack is hidden, for example, by a label, a patient or administering professional may be unaware of the loss of sterility. In the typical strengthened and critically-stressed/frangible case (B), when a severe flaw is initiated, complete destruction of the container is assured.

The transition in behavior from sub-critical flaw growth to super-critical flaw growth with increasing central tension is shown in FIG. 4, which is a plot of the probability of particle ejection as a function of central tension CT of the glass. FIG. 4 illustrates the dependence of critical/catastrophic flaw growth in ion exchanged glass as a function of central tension (CT). As the elastic energy stored as CT increases above a threshold value (e.g., CT_(limit) in equation (2)), flaws will propagate unassisted to release the stored energy. The threshold central tension CT_(limit) may be calculated using the Inglis criteria, which relates flaw size to fracture toughness K_(1C), which is given by the equation

K _(1C) =Y·σ·(π·c)^(1/2),  (4)

where Y is a geometric factor for flaw shape, σ is the stress applied to the flaw to allow flaw propagation, and C is the flaw length. For glass, K_(1C) is about 0.7±0.05. The geometric factor Y is about 1.12 for round (half penny) cracks. Flaw length c is assumed to be about one half the thickness of the wall of the glass container. For a container wall having a thickness of 1.1 mm, the theoretical CT_(limit) is calculated to be 15 Mpa using equation (4).

In some embodiments, the threshold central tension CT_(limit) is at least 13 MPa, which is sufficient to cause a single flaw to propagate without lateral branching. For example, in some embodiments, the threshold central tension CT_(limit) may be at least 15 MPa, at least 18 MPa, or even at least 20 MPa, which is sufficient to cause a single flaw to propagate without lateral branching. In those embodiments in which lateral branching of flaws occurs, the central tension is at least 30 MPa. For example, in some embodiments, the CT_(limit) may be at least 35 MPa, at least 40 MPa, at least 45 MPa, or even at least 50 MPa to produce flaw propagation exhibiting lateral branching. The actual values of the CT_(limit) that result in linear self-propagation of flaws and/or lateral branching of flaws may depend upon the thickness of the container wall (i.e., thickness of the glass of the container wall). For example, for wall thicknesses in a range from about 1.0 mm to about 1.2 mm, the central tension must be at least 13 MPa for flaws (which may not be perfectly aligned with the stress field) to linearly self-propagate, and at least about 35 MPa in order for flaws to self-propagate with lateral branching.

For glass containers having a wall thickness in a range from about 0.5 mm to about 1.5 mm, the stored elastic energy SEE, in some embodiments, should be at least about 3.0 MPa·μm (i.e., (CT²/E)·(t−2DOL)·(1−v)≥3.0 MPa·μm) in order for flaws to self-propagate laterally through the container wall. In other embodiments, SEE is at least about 9.5 MPa·μm (i.e., (CT²/E)·(t−2DOL)·(1−v)≥9.5 MPa·μm) to laterally self-propagate with minimal delay between insult and separation. In other embodiments, SEE is at least 15.0 MPa·μm (i.e., (CT²/E)·(t−2DOL)·(1−v)≥15.0 MPa·μm) to laterally self-propagate flaws with branching through the container wall. Table 1 lists three different levels of flaw propagation and the respective central tension, integrated central tension and stored elastic energy associated with each type of behavior.

TABLE 1 Levels of flaw propagation and central tension, integrated central tension, and stored elastic energy associated with each level. CT ICT SEE Level (MPa) (MPa · μm) (MPa · μm) 1 Flaw propagation, some 13 15000 3.0 delayed 2 Flaw propagation, no delay 30 30000 9.5 or short delay 3 Flaw propagation, 45 42000 15.0 bifurcation

Types of damage incurred by glass containers depend in part upon the central tension CT within the glass and the amount of insult force applied to the glass. Possible breakage modes are shown in a schematic plot of insult force versus central tension in FIG. 5. FIG. 5 is meant to illustrate broad, qualitative behavior trends and is not intended to show well-defined force boundaries between the observed fracture states. In fact, the boundaries are quite diffuse and substantial overlap between regions is known to occur. In general, the types of damage observed may be placed in one of three categories. First, a flaw may be introduced, but the depth of the flaw is less than the thickness of the container wall (region A in FIG. 5). This may result in some surface abrasion or “scuffing” of the surface of the container wall, and occurs at lower insult forces (“insult severity” in FIG. 5) and in instances where the central tension is below a critical value CT_(critical). With increasing insult force, flaws having depths that are greater than the wall thickness are introduced into the glass container (region B in FIG. 5), resulting in through-cracks and breach of container integrity, but not necessarily breakage. As CT increases, greater force must be applied to the container wall to introduce flaws that will result in through-cracks. This is represented by the boundary between the behaviors described in regions A and B, which is approximated by line 1 in FIG. 5. At higher insult forces (approximated by line 2 in FIG. 5), the glass container separates or breaks into multiple pieces (region C in FIG. 5). Beyond a maximum central tension CT_(Max) (line 5 in FIG. 5) insult results in frangible behavior of (i.e., explosive or energetic breakage and ejection of fragments) of the glass (region F in FIG. 5).

Beyond CT_(critical), through-cracks generally do not occur and damage is characterized by either breakage/separation of the container (region D in FIG. 5) or by the introduction of flaws that do not penetrate the thickness of the container wall (region E in FIG. 5), with the boundary between the two damage regimes approximated by line 1.

The failure mode rate of non-ion exchanged borosilicate glass vials is plotted as a function of insult level—expressed here as drop height—in FIG. 9. As the level of insult increases, the rate of failure increases.

Borosilicate glasses (ASTM E438-92 (Standard Specification for Glasses in Laboratory Apparatus) Type 1, class A glasses-3.3 ppm/K, Type 1, class B glasses-5.1 ppm/K) that are typically used as containers for pharmaceuticals, serum, vaccines, and the like may only be strengthened to achieve a central tension CT₁ (line 3 in FIG. 5) that is below CT_(critical) when ion exchanged for periods that are typically used. To obtain a central tension CT₁ that is greater than CT_(critical), such glasses must be ion exchanged for at least 100 hours, which is regarded as unpractical. Such glasses are thus subject to the damage regime in which flaws may result in through-cracks, but no breakage (region B), even though this behavior may be at a low (<10%) frequency. Consequently, a breach of the container wall and compromise of the container's contents may not be detected. In contrast, the glasses described herein may be strengthened to achieve a central tension CT₂ (line 4 in FIG. 5) that is greater than CT_(critical), and will thus be subject to damage regimes in which the container is either not compromised (the flaw depth is less than the thickness of the container) or breaks.

In some embodiments, the container comprises at least one aluminosilicate glass. In particular embodiments, the aluminosilicate glass comprises at least one alkali metal oxide. In some embodiments the container comprises a glass composition that is within the ASTM standard type 1b glass compositions.

In some embodiments, the glass container comprises a chemically durable glass such as that described in U.S. patent application Ser. No. 13/660,141, filed Oct. 25, 2012, by Melinda Drake et al., entitled “Alkaline Earth Alumino-Silicate Glass Compositions with Improved Chemical and Mechanical Durability,” which claims priority from U.S. Provisional Patent Application No. 61/551,133, filed Oct. 25, 2011, and having the same title. The contents of both applications are incorporated herein by reference in their entirety. This exemplary glass composition generally includes SiO₂, Al₂O₃, at least one alkaline earth oxide, and alkali oxides including at least Na₂O and K₂O. In some embodiments, the glass compositions may also be free from boron and compounds containing boron. The combination of these components enables a glass composition which is resistant to chemical degradation and is also suitable for chemical strengthening by ion exchange. In some embodiments, the glass compositions may further comprise minor amounts of one or more additional oxides such as, for example, SnO₂, ZrO₂, ZnO, or the like, which may be added as fining agents and/or to further enhance the chemical durability of the glass composition. In some embodiments, the glasses described therein include from about 67 mol % to about 75 mol % SiO₂; from about 6 mol % to about 10 mol % Al₂O₃; from about 5 mol % to about 12 mol % alkali oxide; and from about 9 mol % to about 15 mol % of alkaline earth oxide. The alkali oxide comprises at least Na₂O and K₂O. In other embodiments, the glasses described therein comprise from about 67 mol % to about 75 mol % SiO₂; from about 6 mol % to about 10 mol % Al₂O₃; from about 5 mol % to about 12 mol % alkali oxide; and from about 9 mol % to about 15 mol % of alkaline earth oxide. The alkaline earth oxide comprises at least one of SrO and BaO.

In some embodiments, the glass container comprises a chemically durable glass such as that described in described in U.S. patent application Ser. No. 13/660,450, filed Oct. 25, 2012, by Paul S. Danielson et al., entitled “Glass Compositions with Improved Chemical and Mechanical Durability,” which claims priority from U.S. Provisional Patent Application No. 61/551,163, filed Oct. 25, 2011, and having the same title. The contents of both applications are incorporated herein by reference in their entirety. The alkali aluminosilicate glass generally includes SiO₂, Al₂O₃, at least one alkaline earth oxide, and one or more alkali oxides, such as Na₂O and/or K₂O, and is free from boron and compounds containing boron. The alkali aluminosilicate glass composition may also be free from phosphorous and compounds containing phosphorous. The combination of these components enables a glass composition which is resistant to chemical degradation and is also suitable for chemical strengthening by ion exchange. In some embodiments the glass compositions may further comprise minor amounts of one or more additional oxides such as, for example, SnO₂, ZrO₂, ZnO, TiO₂, As₂O₃ or the like, which may be added as fining agents and/or to further enhance the chemical durability of the glass composition. In some embodiments, such glasses may include from about 67 mol % to about 78 mol % SiO₂; from about 3 mol % to about 13 mol % alkaline earth oxide; X mol % Al₂O₃; and Y mol % alkali oxide. The alkali oxide comprises Na₂O in an amount greater than 8 mol % and a ratio of Y:X which is greater than 1. In other embodiments, such glasses may comprise from about 67 mol % to about 78 mol % SiO₂; from about 3 mol % to about 13 mol % alkaline earth oxide, wherein the alkaline earth oxide comprises CaO in an amount greater than or equal to 0.1 mol % and less than or equal to 1.0 mol %; X mol % Al₂O₃, wherein X is greater than or equal to 2 mol % and less than or equal to about 10 mol %; Y mol % alkali oxide, wherein a ratio of Y:X is greater than 1. The glass compositions described in U.S. Provisional Patent Applications Nos. 61/551,163 and 61/551,133 are free from boron and compounds of boron and ion exchangeable, thereby facilitating chemically strengthening the glass to improve mechanical durability.

In other embodiments, the alkali aluminosilicate glass comprises: from about 64 mol % to about 68 mol % SiO₂; from about 12 mol % to about 16 mol % Na₂O; from about 8 mol % to about 12 mol % Al₂O₃; from 0 mol % to about 3 mol % B₂O₃; from about 2 mol % to about 5 mol % K₂O; from about 4 mol % to about 6 mol % MgO; and from 0 mol % to about 5 mol % CaO; wherein: 66 mol %≤SiO₂+B₂O₃+CaO≤69 mol %; Na₂O+K₂O+B₂O₃+MgO+CaO+SrO>10 mol %; 5 mol %≤MgO+CaO+SrO≤8 mol %; (Na₂O+B₂O₃)—Al₂O₃≥2 mol %; 2 mol %≤Na₂O—Al₂O₃≤6 mol %; and 4 mol %≤(Na₂O+K₂O)—Al₂O₃≤10 mol %. The glass is described in U.S. Pat. No. 7,666,511 by Adam J. Ellison et al., entitled “Down-Drawable, Chemically Strengthened Glass for Cover Plate,” filed Jul. 27, 2007, and claiming priority to U.S. Provisional Patent Application No. 60/930,808, filed on May 18, 2007, the contents of which are incorporated herein by reference in their entirety.

In other embodiments, the alkali aluminosilicate glass comprises: at least one of alumina and boron oxide, and at least one of an alkali metal oxide and an alkali earth metal oxide, wherein −15 mol %≤(R₂O+R′O—Al₂O₃— ZrO₂)—B₂O₃≤4 mol %, where R is one of Li, Na, K, Rb, and Cs, and R′ is one of Mg, Ca, Sr, and Ba. In some embodiments, the alkali aluminosilicate glass comprises: from about 62 mol % to about 70 mol. % SiO₂; from 0 mol % to about 18 mol % Al₂O₃; from 0 mol % to about 10 mol % B₂O₃; from 0 mol % to about 15 mol % Li₂O; from 0 mol % to about 20 mol % Na₂O; from 0 mol % to about 18 mol % K₂O; from 0 mol % to about 17 mol % MgO; from 0 mol % to about 18 mol % CaO; and from 0 mol % to about 5 mol % ZrO₂. The glass is described in U.S. Pat. No. 8,158,543 by Matthew J. Dejneka et al., entitled “Glasses Having Improved Toughness and Scratch Resistance,” filed Nov. 25, 2008, and claiming priority to U.S. Provisional Patent Application No. 61/004,677, filed on Nov. 29, 2008, the contents of which are incorporated herein by reference in their entirety.

In other embodiments, the alkali aluminosilicate glass comprises: from about 60 mol % to about 70 mol % SiO₂; from about 6 mol % to about 14 mol % Al₂O₃; from 0 mol % to about 15 mol % B₂O₃; from 0 mol % to about 15 mol % Li₂O; from 0 mol % to about 20 mol % Na₂O; from 0 mol % to about 10 mol % K₂O; from 0 mol % to about 8 mol % MgO; from 0 mol % to about 10 mol % CaO; from 0 mol % to about 5 mol % ZrO₂; from 0 mol % to about 1 mol % SnO₂; from 0 mol % to about 1 mol % CeO₂; less than about 50 ppm As₂O₃; and less than about 50 ppm Sb₂O₃; wherein 12 mol %≤Li₂O+Na₂O+K₂O≤20 mol % and 0 mol %≤MgO+CaO≤10 mol %. The glass is described in U.S. patent application Ser. No. 12/392,577 by Sinue Gomez et al., entitled “Fining Agents for Silicate Glasses,” filed Feb. 25, 2009, and claiming priority to U.S. Provisional Patent Application No. 61/067,130, filed on Feb. 26, 2008, the contents of which are incorporated herein by reference in their entirety.

In other embodiments, the alkali aluminosilicate glass comprises SiO₂ and Na₂O, wherein the glass has a temperature T_(35kp) at which the glass has a viscosity of 35 kilo poise (kpoise), wherein the temperature T_(b), at which zircon breaks down to form ZrO₂ and SiO₂ is greater than T_(35kp). In some embodiments, the alkali aluminosilicate glass comprises: from about 61 mol % to about 75 mol % SiO₂; from about 7 mol % to about 15 mol % Al₂O₃; from 0 mol % to about 12 mol % B₂O₃; from about 9 mol % to about 21 mol % Na₂O; from 0 mol % to about 4 mol % K₂O; from 0 mol % to about 7 mol % MgO; and 0 mol % to about 3 mol % CaO. The glass is described in U.S. patent application Ser. No. 12/856,840 by Matthew J. Dejneka et al., entitled “Zircon Compatible Glasses for Down Draw,” filed Aug. 10, 2010, and claiming priority to U.S. Provisional Patent Application No. 61/235,762, filed on Aug. 29, 2009, the contents of which are incorporated herein by reference in their entirety.

In other embodiments, the alkali aluminosilicate glass comprises at least 50 mol % SiO₂ and at least one modifier selected from the group consisting of alkali metal oxides and alkaline earth metal oxides, wherein [(Al₂O₃ (mol %)+B₂O₃ (mol %))/(Σalkali metal modifiers (mol %))]>1. In some embodiments, the alkali aluminosilicate glass comprises: from 50 mol % to about 72 mol % SiO₂; from about 9 mol % to about 17 mol % Al₂O₃; from about 2 mol % to about 12 mol % B₂O₃; from about 8 mol % to about 16 mol % Na₂O; and from 0 mol % to about 4 mol % K₂O. The glass is described in U.S. patent application Ser. No. 12/858,490 by Kristen L. Barefoot et al., entitled “Crack And Scratch Resistant Glass and Enclosures Made Therefrom,” filed Aug. 18, 2010, and claiming priority to U.S. Provisional Patent Application No. 61/235,767, filed on Aug. 21, 2009, the contents of which are incorporated herein by reference in their entirety.

In other embodiments, the alkali aluminosilicate glass comprises SiO₂, Al₂O₃, P₂O₅, and at least one alkali metal oxide (R₂O), wherein 0.75≤[(P₂O₅ (mol %)+R₂O (mol %))/M₂O₃ (mol %)]≤1.2, where M₂O₃=Al₂O₃+B₂O₃. In some embodiments, the alkali aluminosilicate glass comprises: from about 40 mol % to about 70 mol % SiO₂; from 0 mol % to about 28 mol % B₂O₃; from 0 mol % to about 28 mol % Al₂O₃; from about 1 mol % to about 14 mol % P₂O₅; and from about 12 mol % to about 16 mol % R₂O; and, in certain embodiments, from about 40 to about 64 mol % SiO₂; from 0 mol % to about 8 mol % B₂O₃; from about 16 mol % to about 28 mol % Al₂O₃; from about 2 mol % to about 12% P₂O₅; and from about 12 mol % to about 16 mol % R₂O. The glass is described in U.S. patent application Ser. No. 13/305,271 by Dana C. Bookbinder et al., entitled “Ion Exchangeable Glass with Deep Compressive Layer and High Damage Threshold,” filed Nov. 28, 2011, and claiming priority to U.S. Provisional Patent Application No. 61/417,941, filed Nov. 30, 2010, the contents of which are incorporated herein by reference in their entirety.

In still other embodiments, the alkali aluminosilicate glass comprises at least about 4 mol % P₂O₅, wherein (M₂O₃ (mol %)/R_(x)O(mol %))<1, wherein M₂O₃=Al₂O₃+B₂O₃, and wherein R_(x)O is the sum of monovalent and divalent cation oxides present in the alkali aluminosilicate glass. In some embodiments, the monovalent and divalent cation oxides are selected from the group consisting of Li₂O, Na₂O, K₂O, Rb₂O, Cs₂O, MgO, CaO, SrO, BaO, and ZnO. In some embodiments, the glass comprises 0 mol % B₂O₃. The glass is described in U.S. patent application Ser. No. 13/678,013, filed Nov. 15, 2012, by Timothy M. Gross, entitled “Ion Exchangeable Glass with High Crack Initiation Threshold,” and claiming priority to U.S. Provisional Patent Application No. 61/560,434, filed Nov. 16, 2011, the contents of which are incorporated herein by reference in their entirety.

In still other embodiments, the alkali aluminosilicate glass comprises at least about 50 mol % SiO₂ and at least about 11 mol % Na₂O, and the compressive stress is at least about 900 MPa. In some embodiments, the glass further comprises Al₂O₃ and at least one of B₂O₃, K₂O, MgO and ZnO, wherein −340+27.1.Al₂O₃−28.7.B₂O₃+15.6.Na₂O−61.4.K₂O+8.1·(MgO+ZnO)≥0 mol %. In particular embodiments, the glass comprises: from about 7 mol % to about 26 mol % Al₂O₃; from 0 mol % to about 9 mol % B₂O₃; from about 11 mol % to about 25 mol % Na₂O; from 0 mol % to about 2.5 mol % K₂O; from 0 mol % to about 8.5 mol % MgO; and from 0 mol % to about 1.5 mol % CaO. The glass is described in U.S. patent application Ser. No. 13/533,296, by Matthew J. Dejneka et al., entitled “Ion Exchangeable Glass with High Compressive Stress,” filed Jun. 26, 2012, and claiming priority from U.S. Provisional Patent Ion Application No. 61/503,734, filed Jul. 1, 2011, the contents of which are incorporated herein by reference in their entirety.

In other embodiments, the alkali aluminosilicate glasses described hereinabove are ion exchangeable and comprise at least about 50 mol % SiO₂; at least about 10 mol % R₂O, wherein R₂O comprises Na₂O; Al₂O₃, wherein Al₂O₃ (mol %)<R₂O (mol %); and B₂O₃, and wherein B₂O₃ (mol %)-(R₂O (mol %)-Al₂O₃ (mol %))≥3 mol %. In some embodiments, the glass comprises: at least about 50 mol % SiO₂, from about 9 mol % to about 22 mol % Al₂O₃; from about 3 mol % to about 10 mol % B₂O₃; from about 9 mol % to about 20 mol % Na₂O; from 0 mol % to about 5 mol % K₂O; at least about 0.1 mol % MgO, ZnO, or combinations thereof, wherein 0≤MgO≤6 and 0≤ZnO≤6 mol %; and, optionally, at least one of CaO, BaO, and SrO, wherein 0 mol %≤CaO+SrO+BaO≤2 mol %. These glasses are described in U.S. Provisional Patent Application No. 61/653,489, filed May 31, 2012, by Matthew J. Dejneka et al., and entitled “Zircon Compatible, Ion Exchangeable Glass with High Damage Resistance,” the contents of which are incorporated herein by reference in their entirety.

In other embodiments, the alkali aluminosilicate glasses described hereinabove are ion exchangeable and comprise: at least about 50 mol % SiO₂; at least about 10 mol % R₂O, wherein R₂O comprises Na₂O; Al₂O₃, wherein −0.5 mol %≤Al₂O₃ (mol %) —R₂O (mol %)≤2 mol %; and B₂O₃, wherein B₂O₃ (mol %)-(R₂O (mol %)-Al₂O₃ (mol %))≥4.5 mol %. In some embodiments, the glasses comprise: at least about 50 mol % SiO₂, from about 12 mol % to about 22 mol % Al₂O₃; from about 4.5 mol % to about 10 mol % B₂O₃; from about 10 mol % to about 20 mol % Na₂O; from 0 mol % to about 5 mol % K₂O; at least about 0.1 mol % MgO, ZnO, or combinations thereof, wherein 0 mol %≤MgO≤6 and 0≤ZnO≤6 mol %; and, optionally, at least one of CaO, BaO, and SrO, wherein 0 mol %≤CaO+SrO+BaO≤2 mol %. These glasses are described in U.S. Provisional Patent Application No. 61/653,485, filed May 31, 2012, by Matthew J. Dejneka et al., and entitled “Ion Exchangeable Glass with High Damage Resistance,” the contents of which are incorporated herein by reference in their entirety.

In some embodiments, the alkali aluminosilicate glasses described hereinabove are substantially free of (i.e., contain 0 mol % of) of at least one of lithium, boron, barium, strontium, bismuth, antimony, and arsenic.

In some embodiments, the alkali aluminosilicate glasses described hereinabove are down-drawable by processes known in the art, such as slot-drawing, fusion drawing, re-drawing, and the like, and has a liquidus viscosity of at least 130 kilopoise. In some embodiments, the alkali aluminosilicate glasses described hereinabove are suitable for tube drawing and re-forming from tubes and the like and have a liquidus viscosity of at least 10 kilopoise and, in some embodiments, at least about 40 kilopoise.

In another aspect, a method of making the glass article and container described hereinabove is provided. A glass having a first surface and a second surface separated by a thickness is first provided. The glass may comprise those compositions previously described herein, and be formed by those methods known in the art such as, but not limited to, down-drawing, including slot and/or fusion drawing, float methods, casting methods, molding processes such as, but not limited to, Vello, Danner, and blow-molding processes, or the like. A first region under compressive stress (compressive layer) extending from at least one surface of the glass to a depth of layer into the glass is formed using those means previously described herein, such as thermal tempering, chemical strengthening by ion exchange, lamination, or application of coatings to the surface of the glass. The formation of the regions under compressive stress in turn forms a second region in the glass that is under a tensile stress (central tension) as previously described herein. The central tension is sufficient to cause the self-propagation of a flaw from the first surface through the thickness of the glass article to the second surface and laterally across at the first surface and, in some embodiments, the second surface of the glass. In some embodiments, the central tension is greater than a threshold value of at least 13 MPa. In some embodiments, the central tension is greater than or equal to a threshold value of at least 15 MPa, at least 18 MPa, or even at least 20 MPa. In other embodiments, the central tension is sufficient to cause lateral flaw branching and/or is greater than a threshold value of at least 30 MPa, in some embodiments, at least 35 MPa, and in still other embodiments, at least 50 MPa. For glass containers having a wall thickness in a range from about 0.5 mm to about 1.5 mm, the stored elastic energy SEE associated with the central tension, in some embodiments, is at least 3.0 MPa·μm in order for flaws to self-propagate with lateral branching through the container wall. In other embodiments, SEE is at least 9.5 MPa·μm, and, in still other embodiments, SEE is at least 15.0 MPa·μm. The self propagation of the flaw renders the glass article unsuitable for its intended use. Such intended uses include, but are not limited to, containers for substances, such as pharmaceuticals or the like, for which hermeticity and/or sterility are desired.

In another aspect, a method of ensuring self-elimination of a vessel having an intended use is provided. The method comprises providing the vessel, wherein the vessel comprises at least one glass and has a thickness and first surface and a second surface. As previously described hereinabove, the glass has a first region under a compressive stress, the first region extending from at least one of the first surface and the second surface to a depth of layer in the glass, and a second region under a tensile stress, the second region extending from the depth of layer. The central tension is greater than a threshold tensile stress that is sufficient to allow self-propagation of a flaw front through the thickness from the first surface to the second surface and lateral flaw propagation across the first surface and, in some embodiments, across the second surface. In some embodiments, the central tension is greater than a threshold value of at least 13 MPa. In some embodiments, the central tension is greater than or equal to 15 MPa, greater than or equal to 18 MPa, or even greater than or equal to 20 MPa. In other embodiments, the central tension is sufficient to cause lateral flaw branching and/or is greater than a threshold value of at least 30 MPa, in some embodiments, at least 35 MPa, and in still other embodiments, at least 50 MPa. For glass containers having a wall thickness in a range from about 0.5 mm to about 1.5 mm, the stored elastic energy SEE associated with the central tension, in some embodiments, is at least 11 J/m² in order for flaws to self-propagate with lateral branching through the container wall. In other embodiments, SEE is at least 13 J/m². The self-propagation of the flaw front laterally across the first surface, including bifurcation, renders the vessel unsuitable for its intended use.

As used herein, the terms “self-elimination,” “failure,” “unsuitable for (its) intended use,” and the like mean that, after receiving an insult (e.g., impact), the contents of the container is exposed to the elements outside the container. Whether such exposure occurs is determined by those means known in the art, such as, for example, dye ingress testing. In dye ingress testing, the container to be tested is partially filled with clean, colorless water, and the container is closed and sealed as it would be in a commercial setting (e.g., with a rubber stopper, septa, crimp caps, etc.). The filled and sealed container is then submerged in a concentrated dye solution. Non-limiting examples of the dye include methylene blue, FD&C dyes, or the like. The dye solution and container are evacuated to a vacuum of greater than 20 inches Hg and held in vacuum for 15 minutes, after which the containers are exposed to ambient pressure while under the dye (allowing for ingress) for 15 minutes, then are removed from the dye solution, rinsed, dried, and visually inspected. Any coloration of the water inside the container is classified as a failure. Photospectrometric methods known in the art may be used to improve the accuracy of the visual inspection, and are capable of detecting less than about 2 ppm dye in the container. Another method of maintaining failure is described in ASTM F2338-09, “Standard Test Method for Nondestructive Detection of Leaks in Packages by Vacuum Decay Method,” the contents of which are incorporated by reference in their entirety. In ASTM F2338-09, leaks in the container are detected by measuring the rise in pressure in an enclosed evacuated test chamber containing the container due to leakage and/or volatilization of the liquid contents of the container.

EXAMPLES

The following examples illustrate the features and advantages of the glasses described herein and are in no way intended to limit the disclosure or appended claims thereto.

Example 1: Drop Tests on Borosilicate and Alkali Aluminosilicate Cylindrical Glass Vials

Drop tests were performed on cylindrical borosilicate glass vials (Schott Fiolax® clear) and alkali aluminosilicate glass vials described in U.S. patent application Ser. No. 13/660,450. All vials studied had 3.00 ml nominal volume, 3.70 cm height, 16.75 mm diameter, and 1.1 mm wall thickness. The alkali aluminosilicate glass vials were ion-exchanged in a KNO₃ (technical grade) salt bath at 450° C. for 8 hours. All vials were depyrogenated at 320° C. for 1 hr and cooled to a temperature of less than 90° C. before testing.

The drop tests were conducted as schematically shown in FIG. 6. A first vial 610 (also referred to herein as the “dropped vial”) is dropped from a height d such that a portion of the “heel (i.e., the point at which the wall 612 and base 614 of the vial meet)” 615 of first vial 610 strikes a portion of the side wall 622 of a second vial 620 (also referred to herein as the “bottom vial”) which is horizontally oriented (i.e., placed on its side) and inclined at ˜30° from level. Both dropped vials and bottom vials had the same composition and dimensions. At least thirty vials of each glass (first vial and second vial) were dropped from a height of 8 feet. After impact both the dropped vials and bottom vials were visually inspected for damage. Damage (or failure) was classified as either superficial or “scuffing,” flaws penetrating through the thickness of the vial (“through cracks”), or complete breakage or separation of the vial wall. A vial was deemed to have “survived” the drop test if the vial held and did not leak liquid after the test.

The frequency of each mode of damage (“failure mode rate”) is plotted for dropped and bottom vials is plotted in FIG. 7 for the Type 1b borosilicate glass vials and the ion exchanged alkali aluminosilicate glass vials. The dropped borosilicate vials survived the drop test without breakage/separation at a rate of about 90%, which increases the probability of compromising the integrity of the vial and making loss of integrity difficult to detect. The bottom borosilicate vials survived the drop test without breakage/separation at a rate of about 10%, making any failure that would compromise the integrity of the vial less frequent in the bottom vial. This difference in behavior is due to the drop orientation and stresses experienced during this dynamic drop test. Thus, compromised integrity could be present in about half of the population of the vials tested.

None of the dropped the ion-exchanged alkali aluminosilicate glass vials exhibited a through-crack resulting from the drop test without breakage/separation, thus facilitating detection of any failure that would compromise the integrity of the dropped vial. The bottom ion exchanged alkali aluminosilicate glass vials showed the same behavior (no stable through-cracks) resulting from the drop test without breakage/separation as the dropped vials. When introduced to the alkali aluminosilicate vials, the through-cracks observed in the borosilicate glasses now result in outright breakage/separation. Compromised integrity would therefore be less likely to occur in both dropped and bottom vials of the ion exchanged alkali aluminosilicate glass, as those borosilicate glass containers having a likelihood of compromised integrity have been converted to “broken/separated” or “scuffed” in the ion exchanged alkali aluminosilicate glass population.

The failure mode of the ion exchanged alkali aluminosilicate glass vials is plotted as a function of central tension in FIG. 8. The vials were ion-exchanged in a KNO₃ salt bath at 450° C. The percentage of samples that do not fail due to breakage/separation decreases from about 75% after ion exchange for less than one hour to a minimum of about 18% after ion exchange for about 15 hours. The failure (breakage/separation) rate remains relatively stable, ranging from about 70% to about 18% for central tensions ranging from about 10 MPa to about 37 MPa, which corresponds to ion exchange times ranging from 6.6 to 48 hours. As shown in FIG. 8, the vials having a CT of about 13.8 MPa exhibited propagation of flaws through the thickness of the glass, which resulted in cracks extending from the first surface of the glass to the second surface of the glass. This indicates that a CT of at least 13.8 MPa is sufficient to cause flaws extending into the CT region of the glass to propagate all the way through the glass. Thus, self-propagation of flaws through the thickness of the glass and laterally across at least one surface of the glass begins to occurs when the CT is greater than at least 13.8 MPa, based on the data presented in FIG. 8. Similarly, the number of samples that undergo delayed failure decreases with ion exchange time due to acceleration of crack propagation caused by increased central tension. Additionally, at CT values just above the threshold central tension (e.g., CT values just above 13 MPa), flaws may propagate at some time following the drop test (damage introduction), referred to as “delayed failure.” The time to failure is less than 24 hours near the threshold CT. At slightly higher CT values, the time to failure decreases to less than one hour and, in some instances, even less than one minute. Even with delayed failure, the flaws penetrating into the central tension region of the glass are never “stable.” Once the flaw begins propagating due to the central tension, the flaw continues to propagate without stopping, which leads to a condition in which the vial cannot hold fluid (i.e., separation/breakage).

Example 2: Flaw Propagation in 2 ml Vials in Response to Deep Damage

In Example 2, three milliliter (mL) vials were ion exchanged under varying conditions to produce glass vials with a range of central tension (CT) values. The flaw propagation behavior of the glass vials in response to deep through cut damage introduced with a precision circular saw was studied. The 3 mL glass vials had a wall thickness of 1.1 mm. Three milliliter (mL) borosilicate glass vials were used for Comparative Example CE2-1. The borosilicate glass vials of Comparative Example CE2-1 were not subjected to ion exchange. A second group of Comparative Examples CE2-2 included 3 ml alkali aluminosilicate glass vials, such as those described in U.S. patent application Ser. No. 13/660,450. The vials of Comparative Example CE2-2 were not subjected to ion exchange.

For each of Examples 2-1 through 2-20, a plurality of 3 mL alkali aluminosilicate glass vials, such as those described in U.S. patent application Ser. No. 13/660,450, were ion-exchanged in a bath of molten potassium nitrate (KNO₃) under conditions sufficient to produce the compressive stresses, central tensions, and depths of layer listed in Table 2. The sample vials for Example 2-2 were subjected to a supplemental re-annealing step prior to ion exchange to further increase the CS of the glass vials and to evaluate the effects of increasing the CS on the flaw propagation behavior of the glass vials. It is noted that all of the vials and cartridges in Examples 2 through 4 were subjected to an initial post-manufacturing annealing step to homogenize the stresses from the converting process. After the initial post-manufacturing annealing step, the vials of Example 2-2 were further subjected to the supplemental re-annealing step at a temperature of 630° C. for a period of about 2 hours. As shown in Table 2, the combination of re-annealing and ion exchange produced an average CS of 776 MPa for the vials of Example 2-2.

Following ion exchange, the glass vials of Examples 2-1 through 2-20 were evaluated for compressive stress (CS), central tension (CT), and depth of layer (DOL) according to the test methods previously described herein. For each of Examples 2-1 through 2-20, the CS, CT, and DOL of the samples vials were averaged together to produce an average CS (CS_(A)), an average CT (CT_(A)), and an average DOL (DOL_(A)) for each Example. The CS_(A), CT_(A), and DOL_(A) for each of Examples 2-1 through 2-20 are provided below in Table 2.

Following ion exchange, controlled deep damage was introduced to vials of Comparative Examples CE2-1, CE2-2, and the vials of Examples 2-1 through 2-20 using an Accutom-50 precision saw with a Buehler IsoMet 15LC diamond blade. The saw blade had a diameter of 4 inches (102 mm) and a thickness of 0.2 millimeters (mm). The precision saw was used to produce deep damage in the sidewall of each vial. The precision saw was operated at a slow rotational speed of 300 rpm and included water lubrication of the diamond blade during cutting.

Referring to FIG. 10, a schematic of the testing configuration for introducing the deep through cut damage in Example 2 is depicted and shows the positioning of the saw blade relative to the glass vials. Each of the vials 1002 was placed in a holder 1010 having plastic and rubber contact surfaces 1012 to minimize stress concentrations on the glass vials 1002. Once secured in the holder 1010, each of the vials 1002 was then gradually fed to the precision saw 1020 at a rate of 5 micrometers per second (μm/s). Referring to FIG. 10, each vial 1002 was oriented relative to the saw blade 1022 to produce an axial through-cut 1024 (i.e., extending in the +/−Z direction of the coordinate axis of FIG. 10) at the center C of the sidewall 1004. As shown in FIG. 10, the center C of the sidewall 1004 was located at a vertical position (i.e., a position in the +/−Z direction of the coordinate axis of FIG. 10) halfway between the bottom 1006 and the shoulder 1008 of the vial 1002. The cut depth of the saw was 1.5 mm and the sidewall thickness 1004 of the vials 1002 was 1.1 mm. The cut depth of the precision saw 1020 was measured as the distance from the outer surface 1009 of the vial 1002 to the outer edge 1026 of the saw blade 1022 at the center of the saw cut, which coincided with the center C of the sidewall 1004 of the vial 1002. FIG. 10 also illustrates the flange 1007 of the glass vial 1002.

The introduction of controlled deep damage to the vials using a precision saw according to the previously described method provided a repeatable, conservative measurement of the central tension threshold for flaw propagation. The slow rotational speed, gradual feed, water lubrication, and fine-grained diamond abrasive wheel of the saw blade were selected to reduce the applied stresses which could otherwise affect flaw propagation. Additionally, the low geometric stress intensity factor from the wide width of the saw cut trench, combined with low applied stress from the saw blade and the compliant contact surfaces minimized the likelihood of a false positive result with flaw propagation caused by outside forces.

For each of Comparative Examples CE2-1 and CE2-2 and Examples 2-1 through 2-20, 18 to 20 vials were subjected to controlled deep damage according to the previously described method. The flaw propagation behavior of each of the vials was evaluated during and after introduction of the deep damage. The flaw growth evaluation during and 1 hour after the saw cut are provided below in Table 2. Table 2 includes the percentage of vials for which flaws in the glass did not grow/propagate, the percentage of vials for which flaws propagated through the thickness of the glass and laterally across the glass but arrested at the neck or flange of the vial, and the percentage of vials which exhibited full propagation of the flaws. As used herein, the term “full propagation” refers to propagation of a flaw through the thickness of the glass and propagation of the flaw laterally to an edge of the vial (e.g., all the way through the flange to the very top surface of the flange), back into itself, or into another crack. In Table 2, columns labeled with the term “none” represent the percentage of vials in each example for which flaws in the vial did not propagate through the glass during or after the saw cut. In Table 2, the columns labeled with the term “arrest” include data on the percentage of vials in each example for which flaws propagated through the thickness and laterally across at least the first surface but arrested (i.e., stopped propagating) at a feature (e.g., at the bottom, shoulder, or flange) of the vial without reaching an edge of the vial or propagating back into itself or another crack. In Table 2, the columns labeled “full” represents the percentage of vials for which flaws exhibited full propagation.

TABLE 2 Stress profile and flaw propagation behavior in response to a sidewall saw cut for the glass vials of Comparative Example CE2-2 and Examples 2-1 through 2-20 Stress Profile After Ion Exchange CS_(A) DOL_(A) CT_(A) Flaw Propagation During Saw Cut (%) Flaw Propagation after 1 Hour (%) # (MPa) (μm) (MPa) None Arrest Full None Arrest Full CE2-2 0 0 0 100 0 0 100 0 0 2-1* 227.5 21.6 3.7 100 0 0 100 0 0 2-2 776 11.2 9.3 100 0 0 100 0 0 2-3 653.3 19.4 9.4 40 60 0 40 60 0 2-4* 208.6 60.5 9.7 100 0 0 100 0 0 2-5 650.3 24.4 11.8 13 67 20 0 34 66 2-6 595.6 29.8 13.3 0 53 47 0 0 100 2-7 582.3 34.9 15.3 0 17 83 0 0 100 2-8 658.5 33.8 16.7 0 0 100 0 0 100 2-9 566.3 42.5 18.6 0 23 77 0 0 100 2-10 550.3 50.1 21.0 0 0 100 0 0 100 2-11 578.4 55.1 24.3 0 0 100 0 0 100 2-12 521.0 64.6 25.9 0 0 100 0 0 100 2-13 510.0 69.5 27.4 0 0 100 0 0 100 2-14 577.3 63.8 28.3 0 0 100 0 0 100 2-15 494.5 81.0 31.2 0 0 100 0 0 100 2-16 512.9 80.7 32.2 0 0 100 0 0 100 2-17 352.3 133.9 38.3 0 0 100 0 0 100 2-18 448.5 124.2 44.9 0 0 100 0 0 100 2-19 Immeasurable 42.5 0 0 100 0 0 100 2-20 Immeasurable 56.0 0 0 100 0 0 100 *For samples 2-1 and 2-4, it was observed that 50 wt. % NaNO₃ poisoning occurred during ion exchange.

As shown in Table 2, when the CT of the glass vials is above 13 MPa, 100% of the glass vials experienced full propagation of flaws within 1 hour of introduction of the saw cut deep damage. For example, the vials of Example 2-5 were ion-exchanged to produce a CT of 11.8 MPa. When subjected to the saw cut deep damage, a portion (13%) of the vials of Example 2-5 did not exhibit flaw propagation and did not develop through cracks during the saw cut, and at 1 hour, 34% of the vials experienced flaw propagation that arrested at a feature (e.g., shoulder, neck, flange, etc.) of the vial without continuing to full propagation. In comparison, the vials of Example 2-6 were ion-exchanged to produce a CT of 13.3 MPa. When subjected to the saw cut deep damage, 100% of the vials of Example 2-6 experienced flaw propagation during the saw cut, and 100% of the vials of Example 2-6 exhibited full propagation of the flaws within 1 hour. The vials of Examples 2-7 through 2-20 all had CT values greater than 13 MPa and all exhibited full propagation of flaws within 1 hour after the saw cut.

Full propagation of flaws and through-cracks in the glass vials increases the probability that defective or damaged vials will be identified and removed from inventory to prevent the contents from being administered. For example, full propagation of flaws in the glass vials may cause the damage to the glass vials to be obvious and easily discernable through visual inspection so that the damaged or defective vials can be rejected. In other words, full propagation of the flaws throughout the entire glass articles may enable any damage to be visually evident. Therefore, more expensive and time intensive defect detection methods, such as high voltage leak detection, may not be necessary, and the rate of manufacture and filling of the glass vials and/or glass articles may be increased. Visual evidence of damage that is provided by full propagation of flaws rendering the article unsuitable for its intended use may also enable easy identification of vials damaged after filling and packaging, thereby enabling damaged vials and their contents to be removed from circulation downstream of the filling operation.

The results in Table 2 further demonstrate that flaw propagation is not particularly dependent upon the CS of the glass, beyond the effect of the CS on the CT. For example, the vials of Example 2-2 were re-annealed to increase the CS of the glass vial to 776 MPa, which was the highest CS of Example 2. Despite having the highest CS, the vials of Example 2-2 only exhibited a CT of 9.3. For Example 2-2, 100% of the vials tested exhibited no flaw propagation during the saw cut or within 1 hour after the saw cut. Thus, Example 2-2 demonstrates that flaw propagation behavior of the glass vials is driven primarily by the CT of the glass, and the influence of increasing the CS on the flaw propagation behavior is limited to the resulting increase in CT. CS does not have a substantial independent effect on flaw propagation behavior beyond its influence on the CT of the glass.

Additional qualitative observations of the flaw propagation behavior for Comparative Examples CE2-1 and CE2-2 and Examples 2-1, 2-2, 2-4, 2-8, 2-14, 2-16, 2-17, 2-19, and 2-20 are provided in Table 3. In addition to the sidewall saw cut deep damage described previously in Example 2, groups of vials from CE2-1, CE2-2 and Examples 2-1, 2-2, 2-4, 2-8, 2-14, 2-16, 2-17, 2-19, and 2-20 were subjected to a saw cut positioned at the heel of the glass vial. Referring to FIG. 10, the heel 1030 is the area of the glass vial at the transition between the sidewall 1004 and the bottom 1006 of the glass vial 1002. The method and parameters for performing the heel saw cut were the same as previously described except for the orientation of the glass vials relative to the circular blade of the precision saw. For the heel saw cut, the glass vials were positioned so that an axial centerline of the glass vials formed a 45 degree angle with a line normal to the outer surface 1026 (FIG. 10) of the saw blade 1022 (FIG. 10). In this orientation, the outer surface 1026 of the saw blade 1022 contacted the glass vial 1002 (FIG. 10) at the heel 1030 (FIG. 10) first instead of the sidewall 1004. The flaw propagation behaviors of the glass vials in response to the sidewall saw cuts and the heel saw cuts were observed during and after the saw cuts. The observations of flaw propagation behavior and CT of the glass vials are provided below in Table 3.

In Table 3, the observation of “% propagation” refers to the percentage of vials exhibiting flaw propagation for each Example or Comparative Example. In Table 3, the term “completion” refers to full propagation of the flaws as previously described herein. In Table 3, “separation” refers to separation of the glass vial into a plurality of pieces. In Table 3, the term “branching” refers to the flaw propagation behavior in which the flaws bifurcated into a plurality of cracks (i.e., splitting of the flaw front into a plurality of flaw fronts). The average saw cut depth (ave. saw cut depth) refers to the depth of the saw blade in the glass at the time the crack propagation proceeded to completion, thereby separating the vial into a plurality of pieces.

TABLE 3 CT and flaw propagation behavior in response to a sidewall saw cut deep damage and heel saw cut deep damage for the glass vials of CE2-1, CE2-2 and Examples 2-1, 2-2, 2-4, 2-8, 2-14, 2-16, 2-17, 2-19, and 2-20 % Observations of Flaw Prop Observations of Flaw CT_(A) Propagation Response to Thru Propagation Response to Heel # (MPa) Sidewall Cut Flange Saw Cut CE2-1 0 No flaw propagation  0 No flaw propagation CE2-2 0 No flaw propagation  0 No flaw propagation 2-1 3.7 No flaw propagation  0 No flaw propagation 2-2 9.3* No flaw propagation  0 No flaw propagation 2-4 9.7 45% propagation with crack   45** No flaw propagation arresting in neck or flange in 3 days 2-8 16.7 100% propagation to completion  90 100% propagation to at average saw cut depth of 1.0 mm; completion; 0% branching; ave. separation into 2-3 pieces saw cut depth 1.1 mm; separation into 2 pieces. 2-14 28.3 100% propagation to completion 100 100% propagation to at average saw cut depth of 1.0 mm; completion; 0% branching; ave. separation into 2-5 pieces saw cut depth 1.1 mm; 2 pieces 2-16 32.2 100% propagation to completion 100 100% propagation to at average saw cut depth of 0.9 mm; completion; 0% branching; ave. separation into 4+ pieces saw cut depth 0.8 mm; separation into 2-3 pieces. 2-17 38.3 100% propagation to completion 100 100% propagation to at average saw cut depth of 0.9 mm; completion; 70% branching at separation into 4+ pieces 6-10 mm; ave. saw cut depth 0.8 mm; separation into 2-4 pieces. 2-19 42.5 100% propagation to completion 100 100% propagation to at average saw cut depth of 0.6 mm; completion; 100% branching at separation into 50+ pieces 6-10 mm; ave. saw cut depth 0.5 mm; separation into 50+ pieces. 2-20 56 100% propagation to completion 100 100% propagation to at average saw cut depth of 0.9 mm; completion; 100% branching; separation into 50+ pieces ave. saw cut depth 0.5 mm; separation into 50+ pieces. *Vials for Example 2-2 in Table 2 were further annealed in a supplemental re-annealing step as previously described herein. **Propagation of the cracks through the flange was delayed.

As shown by the flaw propagation results and observations in Table 3, for Examples 2-8, 2-14, 2-16, 2-17, 2-19, and 2-20, the sidewall cut and heel cut resulted in full propagation of flaws to completion and separation of the vials into multiple pieces during the saw cut. For comparison, the glass vials of Example 2-4 had a CT of 9.7 MPa, and did not exhibit flaw propagation within 1 hour. For Example 2-4, only 45% of the vials experienced flaw propagation after 3 days in response to the sidewall cut and none of the vials experienced flaw propagation in response to the heel cut.

As shown in Table 3 for Examples 2-8, 2-14, 2-16, 2-17, 2-19, and 2-20, as the CT of the glass vials increased, the saw depth at which the glass vials experienced full flaw propagation decreased, which indicates that rate of flaw propagation became more rapid with increasing CT. As shown in Table 3, the number of pieces into which the glass vial separated during the saw cut also increased with increasing CT.

Example 3: Flaw Propagation in 2R Vials in Response to Deep Damage

For Example 3, the flaw propagation behavior of smaller 2R glass vials (2 mL vials) in response to deep damage was studied. The 2R vials of Example 3 had a wall thickness of 1.0 mm. The 2R glass vials of Example 3 were alkali aluminosilicate glass vials, such as those described in U.S. patent application Ser. No. 13/660,450, and were subjected to ion exchange in a bath of molten potassium nitrate (KNO₃) under conditions sufficient to produce the compressive stresses (CS_(A)), central tensions (CT_(A)), and depths of layer (DOL_(A)) reported below in Table 4. For each of Examples 3-1 through 3-4, 18 to 20 vials were then subjected to deep sidewall cut damage as previously described in Example 2. Observations of the flaw propagation behavior of the glass vials of Examples 3-1 through 3-4 are provided below in Table 4.

TABLE 4 Stress profile and flaw propagation behavior in response to a sidewall saw cut deep damage for the glass vials of Examples 3-1 through 3-4 Stress Profile After Ion Exchange CS_(A) DOL_(A) CT_(A) Sidewall Saw Cut # (MPa) (μm) (MPa) Flaw Propagation Observations 3-1 595.7 42.3 21.0 100% propagation to completion during test at average cut depth of 0.73 mm. 5% cracks avoided the flange; two-piece axial halves fracture pattern. 3-2 444.8 68.5 26.0 100% propagation to completion through flange during test at average cut depth of 0.74 mm; two- piece cup fracture pattern; 10% separated into more than 2 pieces. 3-3 470.6 72.5 29.2 100% propagation to completion through flange during test at cut depth of 0.75 mm; two-piece cup fracture pattern; 15% separated into more than 2 pieces. 3-4 529.9 70.5 31.9 100% propagation to completion through flange during test at an average cut depth of 0.74 mm; two-piece cup fracture pattern; 20% separated into more than 2 pieces.

In Table 4, “two-piece axial halves fracture pattern” refers to a fracture pattern in which a crack propagates longitudinally through the sidewalls of the glass vial and radially across the bottom so that the vial fractures into two axial halves. The term “cup fracture pattern” refers to a fracture pattern in which a through crack propagates in an angular direction all the way around the circumference of the sidewall to rejoin the crack and/or damage and cause separation of vial into one part that includes the bottom (i.e., the cup) and a second part that includes the flange.

As indicated in Table 4, 100% of the glass vials of Example 3 experienced full propagation of flaws to completion during the test. Comparison of Example 3 to Example 2 demonstrates that the effect of increasing the CT above the threshold CT on self-propagation of flaws penetrating through the DOL occurs for glass vials of various sizes and wall thicknesses. Comparison of Examples 3-1 through 3-4 demonstrates that increasing the CT increases the number of pieces into which the vial separates at full propagation of the flaws.

Example 4: Flaw Propagation in 11.6 mm Cartridges in Response to Deep Damage

In Example 4, 11.6 mm OD cartridges having a wall thickness of 0.95 mm were ion exchanged under varying conditions to produce cartridges with a range of central tension (CT) values. The flaw propagation behavior of the 11.6 mm cartridges in response to a deep damage produced with a precision saw was studied. The cartridges for Comparative Examples CE4-1, CE4-2, and CE4-3 were 11.6 mm borosilicate glass cartridges. The borosilicate glass cartridges of Comparative Examples CE4-1 through CE4-3 were subjected to ion exchange in a bath of molten KNO₃ under the conditions sufficient to produce the central tensions reported in Table 5.

For each of Examples 4-1 through 4-9, a plurality of 11.6 mm glass cartridges produced from alkali aluminosilicate glass, such as the glass compositions described in U.S. patent application Ser. No. 13/660,450, were ion-exchanged in a bath of molten KNO₃ under conditions sufficient to produce the central tensions reported in Table 5. Following ion exchange, the CT of each of the glass cartridges of Comparative Examples CE4-1 through CE4-3 and Examples 4-1 through 4-9 was determined according to the test methods previously described herein. For each Example and Comparative Example, the CT for the sample cartridges were averaged together to produce an average CT (CT_(A)), which is provided below in Table 5. The 11.6 mm glass cartridges of Comparative Examples CE4-1 through CE4-3 and Examples 4-1 through 4-9 had a wall thickness of 0.95 mm.

Controlled deep damage was then introduced to the glass cartridges of Comparative Examples CE4-1 through CE4-3 and the glass cartridges of Examples 4-1 through 4-9 according to the method previously described in Example 2. For each of Comparative Examples CE4-1 through CE4-3 and Examples 4-1 through 4-9, a first group of 18 to 20 sample cartridges were subjected to an axial sidewall cut as described in Example 2, and a second group of 18 to 20 sample cartridges were subjected to an open end cut. FIG. 11 schematically depicts a cartridge 1040. The cartridge 1040 has sidewall 1042, collar 1044, and an open end 1046 positioned at the end of the cartridge 1040 opposite the collar 1044.

For the open end cut, each cartridge 1040 was oriented so that an axial centerline of the cartridge 1040 made a 45 degree angle with a line normal to the outer edge of the saw blade and so that the open end 1046 was positioned towards the saw blade relative to the collar 1044. With the cartridge 1040 in this orientation, the outer edge of the saw blade contacted the open end 1046 of the cartridge 1040 first instead of the sidewall 1042. The 45 degree angle enabled the saw cut damage to be limited to a single point on the open end 1046.

The flaw propagation behavior of each of the cartridges was evaluated during and after introduction of the deep damage. Observations of the flaw propagation behavior for each group of cartridges for Comparative Examples CE4-1 through CE4-3 and Examples 4-1 through 4-9 are provided below in Table 5. In Table 5, the data in columns labeled “None” represent the percentages of cartridges that did not exhibit flaw propagation within 1 hour of imposing the deep damage on the cartridges, the data in the columns labeled “Full: Axial” represent the percentages of cartridges exhibiting full propagation of flaws through the thickness of the glass and axially through the flange, and the data in the columns labeled “Full: Ring-Off” represent the percentages of cartridges exhibiting full propagation of flaws through the thickness of the glass and axially through the cartridge with a ring-off fracture pattern at the flange.

As used herein, the term “ring-off” refers to a fracture pattern of the cartridge in which a crack propagates in an angular direction all the way around the circumference of the sidewall to rejoin the crack and cause separation of a portion of the cartridge resembling a cylindrical ring. A “ring-off” fracture pattern is similar to the cup fracture pattern previously described relative to glass vials. As used herein, the term “spiral ring-off” refers to a fracture pattern in which a crack propagates in the angular direction through greater than 360° but the propagation is slightly in an axial direction so that the crack does not rejoin itself but rather propagates in a spiral along a portion of the sidewall. For a spiral ring-off, in some cases, the entire cartridge may remain connected together. In Table 5, “Full: Ring-Off” includes complete loop ring-off in which the ring is completely separated from the cartridge and spiral ring-off. An “axial crack” refers to a crack that propagates in an axial direction along the sidewall of the cartridge.

TABLE 5 CT and flaw propagation in response to sidewall saw cut deep damage and open end cut deep damage for the cartridges of Comparative Examples CE4-1 through CE4-3 and Examples 4-1 through 4-9 Axial Sidewall Cut (1.5 mm nominal depth) Open End Cut (1.5 mm nominal depth) CT_(A) None Full: Full: None Full: Full: # (MPa) (%) Axial (%) Ring-Off (%) (%) Axial (%) Ring-Off (%) CE4-1 3.4 100 0 0 100 0 0 CE4-2 4.0 100 0 0 100 0 0 4-1* 4.9 100 0 0 100 0 0 CE4-3 6.6 100 0 0 100 0 0 4-2* 8.0 100 0 0 100 0 0 4-3* 13.3 80 20 0 100 0 0 4-4 18.2 0 78 22 100 0 0 4-5 18.9 0 78 22 70 20 10 4-6 24.0 0 60 40 0 70 30 4-7 31.9 0 60 40 0 0 100 4-8 34.3 0 50 50 0 0 100 4-9 37.0 0 40 60 0 60 40 *For Examples 4-1, 4-2, and 4-3, it was observed that 50 wt. % NaNO3 poisoning occurred during ion exchange.

As shown in Table 5, the borosilicate glass cartridges of Comparative Examples CE4-1 through CE4-3 were not able to be ion exchanged enough to create a central tension of greater than 13 MPa. For example, the borosilicate glass cartridge of Comparative Example CE4-3 were ion exchanged at a temperature of 470° C. for an ion exchange time of 25 hours, which only increased the CT of the cartridge of Comparative Example CE4-3 to 6.6 MPa. The alkali aluminosilicate glass cartridges of Examples 4-1 through 4-9 were ion exchanged at lower temperatures and for less time and exhibited greater CT than the glass cartridges of CE4-3. This demonstrates that currently available commercial borosilicate glass compositions may not be capable of being ion exchanged to produce a CT great enough to result in self-propagation of flaw fronts (e.g., of at least 13) in a practical amount of ion-exchange time.

The results in Table 5 also demonstrate that the threshold central tension of 13 MPa may be sufficient to produce self-propagation of flaw fronts through the thickness of the glass and laterally across at least a surface of the glass for glass cartridges, in addition to glass vials. As shown in Table 5, the glass cartridges of Example 4-3 had a CT of 13.3 MPa and exhibit some flaw self-propagation behavior in response to deep damage in the sidewall. As the CT increases above the CT of 13.3 MPa, 100% of the glass cartridges of Examples 4-4 through 4-9 showed full propagation of flaw fronts in response to the deep damage in the sidewall. Thus, the threshold central tension of 13.0 MPa may apply to a plurality of glass articles.

Additionally, the effect of wall thickness on the flaw propagation behavior is shown in Example 4. In Example 4, the cartridges all had a wall thickness at the sidewall of 0.95 mm, which is less than the wall thickness of 1.1 mm of the glass vials in Example 2. As shown by the data in Table 5, full propagation of the flaw fronts in cartridges having a wall thickness of 0.95 mm required a greater CT. For example, the cartridges of Example 4-3 had a CT of 13.3 MPa, but only about half of the cartridges experienced full propagation of flaws within a period of time following introduction of the saw cut damage. For comparison, the cartridges of Example 4-4, which had a CT of 18.2, exhibited full propagation of flaws with no indication of a delay in propagation of the cracks. Thus, for cartridges having a wall thickness of about 0.95 mm, self-propagation of cracks may occur in cartridges having a CT greater than or equal to 18 MPa.

The flaw propagation in response to deep damage at the open end of the cartridge (open end saw cut) was slightly diminished compared to flaw propagation in response to the sidewall cut. Not intending to be bound by any particular theory, it is believed that processing of the glass at the open end may result in a non-linear distribution of CT at the open end of the cartridge. For example, in some cases, the cartridge may include a thicker “elephant foot” bulge around the open end of the cartridge resulting in a non-linear thickness profile of the glass at the open end of the cartridge.

While typical embodiments have been set forth for the purpose of illustration, the foregoing description should not be deemed to be a limitation on the scope of the disclosure or appended claims. Accordingly, various modifications, adaptations, and alternatives may occur to one skilled in the art without departing from the spirit and scope of the present disclosure or appended claims. 

1. A method of making a glass article having a first surface and a second surface separated by a thickness, the method comprising: forming a first region in at least one surface the glass, wherein the first region extends from at least one of the first surface and the second surface to a depth of layer in the glass, and wherein the first region is under a compressive stress; and forming a second region under a central tension of at least about 13 MPa, the second region extending from the depth of layer, wherein the central tension is sufficient to allow self-propagation of a flaw front from the first surface to the second surface and laterally across at least the first surface.
 2. The method of claim 1, wherein the self-propagation of the flaw front from the first surface to the second surface and laterally across at least the first surface renders the glass article unsuitable for its intended use.
 3. The method of claim 1, wherein the self-propagation of the flaw front from the first surface to the second surface further comprises bifurcation of the flaw front across at least the first surface.
 4. The method of claim 1, wherein the glass has a Young's modulus E and a Poisson's ratio v, and (CT²/E)·(t−2DOL)·(1−v)≥3.0 MPa·μm, where CT is the central tension, t is the thickness, and DOL is the depth of layer.
 5. The method of claim 1, wherein forming the first region and forming the second region comprise ion exchange strengthening the glass.
 6. The method of claim 1, wherein the central tension is greater than or equal to about 30 MPa.
 7. The method of claim 6, wherein the central tension is greater than or equal to about 45 MPa.
 8. The method of claim 1, wherein the compressive stress is at least about 200 MPa.
 9. The method of claim 1, wherein the depth of layer is at least about 30 μm.
 10. The method of claim 1, wherein the depth of layer is in a range from about 15% to about 25% of the thickness.
 11. The method of claim 1, wherein the thickness is up to about 6 mm.
 12. The method of claim 1, wherein the thickness is in a range from about 0.3 mm to about 2.0 mm.
 13. The method of claim 1, wherein the glass article is a container is adapted to hold a pharmaceutical product, a vaccine, a biologic, a foodstuff, or a solution.
 14. The method of claim 1, further comprising applying a coating to the first region, wherein the coating has a Young's modulus different than the glass.
 15. A method of ensuring self-elimination of a vessel having an intended use, the method comprising: providing the vessel, the vessel comprising a glass, the vessel having a thickness and first surface and a second surface, wherein the glass has a first region under a compressive stress, the first region extending from at least one of the first surface and the second surface to a depth of layer in the glass, and a second region under a central tension of at least 13 MPa, the second region extending from the depth of layer, wherein the central tension is greater than a threshold tensile stress that is sufficient to allow self-propagation of a flaw front through the thickness from the first surface to the second surface, and wherein the self-propagation of the flaw front from the first surface to the second surface renders the vessel unsuitable for its intended use.
 16. The method of claim 15, wherein the self-propagation of the flaw front from the first surface to the second surface further comprises bifurcation of the flaw front across at least the first surface.
 17. A glass article having a first surface and a second surface separated by glass having a thickness of from 1.0 mm to 1.2 mm, wherein the glass is an ion-exchanged aluminosilicate glass comprising at least one alkali metal oxide and the glass article has a first region under a compressive stress, the first region extending from at least one of the first surface or the second surface to a depth of layer in the glass, and a second region under a central tension greater than 13 MPa, the second region extending from the depth of layer, wherein the central tension is sufficient to allow self-propagation of a flaw front from the first surface to the second surface and laterally across the first surface.
 18. The method of claim 17, wherein the glass has a Young's modulus E and a Poisson's ratio v, and (CT²/E)·(t−2DOL)·(1−v)≥3.0 MPa·μm, where CT is the central tension, t is the thickness, and DOL is the depth of layer. 